This invention relates to an optical, image producing device.
Drawing aids, known as Camera Lucidas, have been proposed comprising two mirrors which are firmly mounted on an inclined drawing board, see, for example, U.S. Pat. No. 3,227,043, Jan. 4, 1966, E. J. Swimmer et al, and U.S. Pat. No. 3,357,769, dated Dec. 12, 1967, K. B. Thompson. The mirrors comprise an upper one, which is inclined, for reflecting an image on to a second semi-transparent mirror, through which the drawing board is seen. By this means, an image reflected by the upper mirror on to the semi-transparent mirror, is seen as an apparent image on the drawing board. This apparent image can then be drawn on the drawing board.
The mirrors are firmly attached to the drawing board to reduce the possibility of image shift while the apparent image is being traced on the is drawing board.
Swimmer et al, column 2, lines 35-39, teaches that the mirrors are at a fixed angle between them which is one half the angle of the drawing board to the vertical. With these angles it is stated that the center of the field of vision is perpendicular to the drawing board surface and lies on the horizon in the object field.
K. B. Thompson et al teaches that parallax may be substantially eliminated between the virtual image being viewed, i.e. at the beam splitter (semi-transparent mirror), and the drawing board, by moving the upper mirror, or alternatively the upper mirror and the beam splitter (semi-transparent mirror), relative to the drawing board, see column 7, lines 61-63, and column 8, lines 5 to 10.
While the devices of E. J. Swimmer et al and K. B. Thompson et al are useful, applicants have found that if in use the entire device, i.e. mirrors and drawing board, is tilted forwards or backwards as an assembly to accommodate a particular scene or object at a different elevation or gradient from that at which the device is situated, or, as a result of the device being used in a hand held manner, or simply placed on the lap in a seated position, then it is more or less inevitable that the angle between the plane of the drawing surface and the vertical will vary to a greater or lesser extent from the ideal angle to the vertical, taught by Swimmer et al, at which the drawing board can be viewed making distortions in the apparent image unavoidable. Applicant has found that any adjustment of the mirrors to compensate for this distortion caused the apparent image to move from the center of the board and significantly decrease the height of the apparent image.
There is a need for an optical image producing device wherein the angle between the plane, of say, the drawing board and the vertical may be adjusted in a simple manner, when the device is tilted backwards or forwards to suit the attitude of the device in relation to the height at which an object is to be viewed, without incurring significant movement of the apparent image from the center of the board or any significant change in the height of the apparent image.
From an artist""s point of view it is highly desirable, for artistic interpretation of a subject, for the subject to be viewed simultaneously by both eyes to achieve the necessary perceptual appearance of solidity. Known Camera Lucidas proposals use a very restricted viewing aperture in order to produce an image of high definition, and to avoid image shift which would result in tracing inaccuracies. When artistic interpretation is the objective, image shift is not a prime concern, and extreme tracing accuracy is irrelevant and usually detrimental.
There is also a need for a Camera Lucidas device which not only allows the subject to be viewed simultaneously by both eyes, but also allows a wider viewing of the background to the subject giving the image viewed a panoramic effect.
According to the present invention there is provided an optical, image producing device, comprising,
a) a first mirror,
b) a second, semi-transparent mirror,
c) a column having viewing means for viewing a reflected image of a subject, from the rear of the column, at an upper position thereof,
d) mirror mounting means for rigidly securing the first and second mirrors to the column, against movement, in a divergent manner from one another, with the viewing means between them for viewing from their closest ends, and with the first mirror uppermost, so that, in operation, an image of the subject, reflected from the first mirror onto the second mirror, can be seen as the reflected image on the second mirror through the viewing means,
e) a base for rigidly supporting the column in an upright position when the device is in use,
f) an image superimposing panel,
g) panel mounting means, for mounting the panel on the base at different angles of inclination, from the vertical, at which the panel is inclined away from the mirrors at an angle which is about twice the divergent angle between the mirrors, and at which the panel can be viewed through the viewing means, with the said reflected image superimposed thereon, when the base is horizontal or when the device is tilted from that position.
In some embodiments of the present invention the viewing means comprises an aperture in the column of sufficient width through which a reflected image can be viewed simultaneously by both eyes.
In other embodiments of the present invention a hinge is provided attaching the column to the base, and removable means are provided for supporting the column in the upright position, against the base, whereby the column can be stored in a folded or flat position.
The means for supporting the column in the upright position may comprise a mounting block insertable in a lower end of the column.
In other embodiments of the present invention, the panel mounting means comprises a slot in the base, and steps and risers in the bottom of the slot for holding the panel in different reclining positions in the slot.
In yet other embodiments of the present invention, the panel mounting means comprises a slot in the base, the slot having an upper neck portion for slidably supporting the panel, and a series of panel receiving grooves at the bottom of the slot for securing the panel at different inclined positions in the slot.
The panel mounting means preferably has the capability of mounting the panel, at the said angles of inclination from the vertical, in the range of about 10xc2x0 to about 60xc2x0.
Better still, the panel mounting means preferably has the capability of mounting the panel, at a said angle of inclination from the vertical, in the range of about 10xc2x0 to about 45xc2x0, when the device is used with the base extending horizontally.
Better still yet, the panel mounting means preferably has the capability of mounting the panel at a said angle of inclination in the range of about 35xc2x0 to about 45xc2x0, when the device is used with the base extending horizontally.